\begin{align*}
R = 
\[ \left( \begin{array}{cccc}
          1.0 & 0.0   &  0.0   & 0.0 \\
          0.0 & 0.866 & -0.5   & 0.0 \\
          0.0 & 0.5   &  0.866 & 0.0 \\ 
          0.0 & 0.0   &  0.0   & 1.0 \end{array} 
\right)\] 
\end{align*}